This proposal addresses the relationship between gender-based violence (GBV) and several mediating factors thought to increase HIV acquisition risk among African women. Prospective studies indicate that women exposed to GBV have a higher risk of HIV infection, but the mechanisms for this association are not well understood. Women exposed to GBV have higher rates of poor mental health and high-risk sexual behavior, which are known to increase HIV risk. In addition, GBV may cause lower adherence to HIV prevention methods such as pre-exposure prophylaxis (PrEP). Different patterns of GBV experiences may have different psychological or behavioral consequences and may affect HIV risk through different mechanisms. Therefore, a full assessment of these mechanisms will require meaningful GBV classifications that consider variation in the type, frequency, and severity of violence, as well as women's relationship to the perpetrator. In this study, we will develop a pattern-based exposure classification based on detailed GBV histories. We will use this classification to evaluate the effect of GBV on mental health, sexual risk behavior, and PrEP adherence. We will test the following hypotheses: 1) Women exposed to patterns of intense GBV (characterized by type, severity, frequency, duration, and perpetrator) are more likely to experience poor mental health; 2) Women exposed to patterns of intense GBV are more likely to engage in high-risk sexual behavior; and 3) Women exposed to GBV have lower adherence to PrEP. The first two hypotheses will be tested with a cross-sectional study of 300 female sex workers in Mombasa, Kenya. The last hypothesis will be tested with a prospective cohort study of 1,785 HIV-uninfected female members of HIV serodiscordant couples participating in a clinical trial of PrEP efficacy in Kenya and Uganda. We focus on these two groups of high-risk women to ensure that our results have maximum relevance for HIV prevention. This will be the first study to evaluate the association of GBV with PrEP adherence, and the first to characterize GBV patterns and their consequences in female sex workers. Our findings will provide new evidence on the effect of GBV on behavioral and psychological HIV risk factors in African women. For example, experience of severe violence, regardless of perpetrator, may be more strongly associated with substance abuse, while experience of intimate partner violence may increase the risk of unprotected sex, directly increasing HIV risk. Positive findings will inform te development of targeted interventions to address key HIV risk factors based on women's individual patterns of GBV experience. Importantly, negative findings would also be useful, as these would help to redirect interventions away from pathways that are not likely to reduce risk.